"It was not my intention to make a product endorsement," he tells the U.S. government ethics boss.

Secretary of the Treasury Steven Mnuchin conceded he risked an ethics violation when he recently urged parents to send their kids to The Lego Batman Movie, on which he served as an executive producer.

But Mnuchin, in a letter to the U.S. Office of Government Ethics made public on Friday to NBC News, stopped short of issuing a full apology, and argued instead his quip delivered at a forum organized by new-media startup Axios did not amount to a movie recommendation.

"I want to assure you that I was aware of the rule against using public office to promote a particular product, as I specifically acknowledged in the interview, and in responding to the question posted by the interviewer, it was not my intention to make a product endorsement," Mnuchin wrote Walter M. Shaub Jr., director of the government's ethics office.

Mnuchin, who promised no future plugs for The Lego Batman Movie, was interviewed by Axios’s co-founder Mike Allen and was asked about movies in which he had been involved as the event was drawing to a close.

Admitting first that he could run afoul of federal ethics laws, Mnuchin raised eyebrows when he answered, “I’m not allowed to promote anything that I’m involved in. So I just want to have the legal disclosure, you’ve asked me the question, and I am not promoting any product. But you should send all your kids to Lego Batman.”

Mnuchin has an executive producer credit on the film. The Treasury Secretary in his letter said he takes "very seriously" his ethical responsibilities.

"I want to reassure you that I will exercise greater caution to avoid any suggestion that I do not take these important rules seriously," Mnuchin wrote. Critics immediately pounced on Mnuchin’s Lego Batman recommendation, noting that RatPac receives income from the film and Mnuchin may not yet be fully divested of the company, which he has promised to do within 120 days of his Feb. 13 confirmation.